One of the small pleasures of summer is walking outside and picking fresh herbs from the garden (or, perhaps more realistically for city dwellers or those lacking a green thumb, the farmer's market) and plopping them directly into a salad or an omelet. But once winter comes, those fresh herbs are harder to come by—including basil, which is pretty sensitive to cold. And if you do come across fresh basil in the off-season, you want to make it last for as long as possible, because those herbs can be expensive, and it's sad to work with wilted basil.
The best way to do extend the shelf life of basil is to learn how to store basil correctly. And though, like many leafy greens, basil is delicate, there are a couple steps you can take to make sure your basil lasts as long as possible.
If you've got bunches of this fresh herb, your best bet is to store basil, stems and all, "in a vase or Mason jar with an inch or two of water at the bottom, just like a bouquet of flowers," according to Serious Eats. Simply snip off the bases of the stems, put them in the jar, and keep the vase at room temperature in an area with some light, "but out of direct sunlight." It should last for about two weeks.
If you've only got leaves of basil, do not wash that basil before storing it. "In our tests," write the editors of Cook's Illustrated Cookbook: 2,000 Recipes from 20 Years of America's Most Trusted Food Magazine, "washing basil before storage decreased its storage life by half. Instead, gently wrap unwashed basil in a damp paper towel," and put it in your fridge's crisper. "It should keep for up to one week," they explain.
You can also freeze fresh herbs if you think it'll take you longer than a week or two to finish off your stash. As Allison Robicelli explains for this site, mince up the basil and mix with some kind of neutral oil to make a thick paste. Put the mixture in an ice cube tray and pop in the freezer; that way, you can take a cube as you need it throughout the winter—or until you're able to get your hands on some more fresh basil.